1. Field of the Invention
The present invention relates to the setting of jacket pilings used in the offshore drilling industry. More particularly, the present invention relates to devices to assist in the controlled setting of pilings into the sea bed within jacket legs.
2. General Background of the Invention
In the offshore oil industry jacket legs are often used to support a platform on which a drilling rig is placed. The jacket leg sits on the sea bed and pilings are driven into the sea bed through the hollow jacket legs to support the jacket and enable it to withstand wind and wave action so that a stable structure is provided.
Many times, when driving the initial piling, a soft layer is encountered through which the piling readily passes without force from the pile driver. This soft layer combined with the weight of the piling, from 100 to 200 tons, allows the piling to rapidly slide down the jacket leg and into the soft layer oftentimes resulting in damage to the piling, the jacket leg, or complete loss of the piling in the soft layer. The resulting damage and time involved in repair and/or replacement increases the set up time and cost for each jacket. To prevent this rapid sinking or running of the pile into the jacket leg it has been common in the industry to weld stops at intervals along the piling which would encounter the top edge of the jacket and hopefully prevent the pile from running into the jacket leg should a soft layer be encountered. The stops however are not always successful in stopping the pile should it begin to run because of its great weight. The stops often will shear off the pile and cause damage to the pile itself and the jacket leg. It is common that once the first set of stops is sheared off the remaining stops will also be sheared and will not prevent the pile from running down into the jacket leg.
The present invention relates to a clamp which is used to prevent the pile from running into the jacket leg. Utilizing the process and this particular clamp apparatus, time consuming and expensive procedure of welding stops to gradually lower the pile and removal of the stops to lower the pile into the jacket leg becomes unnecessary. The present invention allows controlled descent of the pile into the jacket leg when one of the soft layers in the sea bed is encountered. The following patents may be pertinent in the art:
U.S. Pat. No. 4,372,707 issued to Ostgard, discloses a hydraulic pile installation and removal mechanism for temporary jacking up rigs. Hydraulic jacks are attached to the pilings inside the pile guide. Slip mechanisms are used in conjunction the jacket to allow the pilings to be driven into the soil and also removal of the pilings from the soil and back into the pile guides when movement of the rig to a different location is necessary.
U.S Pat. No. 3,496,728 issued to Slack, discloses an apparatus and method for reinforcing offshore drilling and production platforms. A templet is positioned adjacent the platform and driven into the mud until a mud mat secured to the templet is at the mudline. The driving pipe is removed, the templet is secured to the platform, a piling is then driven into the ocean floor through the templet, and the piling is then clamped to the templet by special hubs for reinforcement of the templet and consequently, the platform.
U.S. Pat. No. 3,422,505 issued to Slemmons, discloses a gripper assembly used to support a base or platform on a column. Inflatable annular tubes are used to force seperate resilient gripping members against the suporting legs for the platform when the annular tubes are inflated.
U.S. Pat. No. 2,870,639 issued to Suderow, discloses a gripper and jack assembly for platforms. Upper and lower gripper shoes, moveably mounted on flexible members, are selectivey controllable by jack asemblies to move caissons down into contact with the sea bottom and raise the platform on the caissons.